Sized paper



amounts of fatty acid yield reaction products which are of negligiblevalue as sizing agents for paper. At the other extreme, the amount offatty acid should not exceed the stoichiometrical equivalent Vof thehydroxyl groups as when a larger amount is used the products are undulydiflicult to disperse in water and therefore are not practical forpapermaking purposes, and in practice the convenient maximum from thepoint of view of dispersibility is about ylo'of this value, particularlyin the case of tertiary amines. Thus, in the case of a dialkanolaminesuch as diethanolamine the maximum amount of fatty acid is best limitedto about 1.8-2.0 mols and in the case of a trialkanolamine such astriethanolamine to about 2.7' mols.

The results improve as the ratio of fatty acid to the amine hydroxylgroups is increased over the minimum value of 0.33 mentioned above. Asharp improvement results when the amount of fatty acid is 50% of thestoichiometric equivalent of the hydroxyl groups of the alkanolamine,and a plateau is reached when the amount of fatty acid is between about2/5 and 5%; of the stoichiometric equivalent. Thus, in the case ofdiethanolamine best results are obtained by the use of between 1.3 and1.7 mols of fatty acid per mol of the amine, and in the case oftriethanolamine between 2.0 and 2.5 mols.

As alkanolamines there may be employed in the practice of the presentinvention any of the water-soluble short-chain secondary and tertiaryalkanolamines, that is, alkanolamines having no chain longer than 6carbon atoms. Suitable secondary amines include diethanolaminediisopropanolamine, 3,3iminobis1propanol, 4,4'- iminobis-l-butanol, and6,6iminobislhexanol. Suitable tertiary amines include such N-alkyldialkanolamines as N-ethyl-diethanolamine, N-propyl-dipropanolamine, andN-methyl-diisopropylamine and trialkanolamines such as triethanolamine,tributanolamine, triisobutanolamine, and trihexanolamine.Y Themonoalkanolamines yield poor sizingrresults and these are 4therefore notincluded within the scope of the present invention. The alkyl or alkanolchains may be of the same or different length and may be branched;moreover, the hydroxyl groups may be primary as in the case ofdiethanolamine, secondary as in the case of diisopropylamine, ortertiary as in the case of the iminobis-t-butanol; We have found,however, that' the reaction of fatty acids with primary hydroxyl groupsis more rapid than with secondary or tertiary hydroxyl' p sizingeffectiveness.

groups and therefore the former type of compound is preferred.

As fatty acids there may be employed straight'chain' saturated acidssuch as hexadecanoic acid and octadecanoic acid and similar but branchedacids obtained by petroleum oxidation. 'It is only necessary for theacid to have a sufficiently long carbon chain to render the estercomposition as a whole suiciently hydrophobic for papermaking purposes,and the invention is not limited to the particular acids mentioned.Unsaturated fatty acids are undesirable but are tolerated in minoramounts. YNeither the particular alkanolamine nor the particular fattyacid is therefore a primary feature of the present invention.

While the fatty acids are preferred, nevertheless esters such as ethylstearate and acid chlorides such as stearoyl chloride may be used. Afterreaction similar ester compositions are obtained and correspond to thoseobtained by the use of free fatty acid, the use of the acid chlorideshowever rendering subsequent additionof a solubilizing acid unnecessary.

It will be understood thatthe reaction products describedV above aregenerally complex mixtures. In the first place, the invention permitsVemployment of mixed amines and mixed long chain fatty acids, which ofitself leads tormixed products. Moreover, fatty acid or fatty acidequivalent reacts according to a. normal distribution curve so that onthe-'assumption that only esteritication occurs, the productis a mixtureof mono and diesters,

in limitation thereof.

where dialkanolamines are employed, and are mono, di and triesters wheretrialkanolamines are employed. Since not all of the fatty acid needreact by way of esteriiication or amidation, the product may contain avariable amount of the fatty acid salt of the alkanolamine ester.Further, there is evidence that Where secondary amines are employed someamide formation may take place resulting in the presence ofalkanolamides or alkanolamide esters. As a result, the products are mostconveniently described in terms of their preparation. Y

Where fatty acids or fatty acid esters are employed as raw materials forthe reaction, the reaction products are converted before use towater-dispersible condition by addition of a mineral or organic,water-soluble, nonoxidizing acid having a dissociation constant notmaterially less than that of acetic acid. Suitable acids includehydrochloric acid, hydrobromic acid, nitric acid, formic acid,phosphoric acid, acetic acid, the chloracetic acids, propionic acid, andglycolic acid. Alternatively, materials such as Aepichlorohydrin anddimethylsulfate and alkyl halides such as ethyl chloride may be usedwhich form acid or acid equivalent during their reaction with theestercomposition. In practice we prefer to use acetic acid or hydrochloricacid, these acids being readily available, non-toxic, and having theparticularly desirable property of forming salts of desirably lowsoftening point so that the step of dispersing the salts in water may beperformed without need ofV autoclave equipment. 'I'he acid isadvantageously stirred into the ester composition while in moltencondition and atleast suiiicicnt is added to'render the compositiondispersible upon agitation with 'hot water. Alternatively, the reactionproduct in molten form may be slowly poured into rapidly agitated hotwater, that is, water having a temperature above the softening point ofthe reaction product. In the case of acetic acid we addfroin 1 to 2 molsper nitrogen atom of the alkanolamine and preferably about 1% to 11/2mols, too little acetic acid causing the sizing results to fall olf. Inthe case of hydrochloric acid only between about 1A and 3/4 mols isnecessary and addition of about 1/3 of a mol produces a composition ofabout the best An excess does not inactivate the size. Where fatty acidchlorides are employed, generally no acid Vneed be separately added.

The acids are best added in concentrated form so as to minimize thelamount of water introduced, thereby minimizinghydrolysis of the esters.Y

The process of the present invention does not preclude the addition ofthe materials customarily added in the course of paper manufacture.Included among these are melaminealdehyde, urea-aldehyde and othercationic resins to improve wet strength, starch, gums, and partiallyhydrolyzed polyacrylamides to improve dry strength, and pigments anddyes.

The invention will be more particularly described by the exampleswhich'follow. The examples illustrate embodiments 'of the invention andare'not to be construed Example 1 The following illustrates thepreparation of various sizes according to the present invention. Y;

The. sizes were prepared by charging technical stearic acid and theindicated alkanolamine into a three-necked ask fitted with a mechanicalstirrer, nitrogen inlet tube, and thermo-meter. In each instance l molof the alkanolamine was taken, and the number of mols of stearic acid isshown Vin the table below. The reactionimixtures were fheated to 200 C.in 45-60 minutes and maintained at that temperature at least until the`acid number dropped to 15, and generally below 10. Terminal acidnumbers `areshown in the table. During the reactions, nitrogen gas waspassed through the flask to minimize discoloration cand to `'sweep outthe water formed. Y

i The products were Vcooled to about C. and vsalt- 4 Orming materialstirred in as shown in the table below.

The ester salts thus formed were dispersed by slowly pouring theproducts into rapidly agitated water at 95 C. so as to form dispersionscontaining 5% solids, which were homogenized hot and then cooled.Details of the method by which the sizes were prepared are shown in thefollowing table.

Fatty Acid Added Size No. Amine 1 Acid F. A. Hours Acid Mols 2 Ratio 3Reacted No.

Name Mols 4 2. 5 0. 83 5. 25 6. 9 HC1 0. 35 2. 0. 67 4. 25 2. 2 HCl 0.35 1. 0. 50 1. 25 5. 9 HC1 0. 25 1. 5 0. 50 1. 25 5. 9 HAC 5 1. 0 1. 50. 50 1. 25 5. 9 Me2SO4 0. 5 2.0 1.0 1.5 1. 5 HC1 0.25 1.5 0.75 1.5 2.5HAU 5 1.0 1. 0 0. 50 l. 0 l. 1 HAC 5 1. 0 2. 0 0. 67 7. 5 13.7 HC1 0.5

1 D EA =diethauolamine; TEA =triethanolamine; TIPA =triisopropanolamine.

2 Per mol of amine.

8 Mols fatty acid divided by number of hydroxyl groups of amine.

Per mol of amine taken.

HAc =acetic acid.

Example 2 The sizes of Example 1 were diluted to 1.5% solids by additionof water and were evaluated as follows.

A 60% :40% bleached sulte-soda pulp mixture beaten to a Green freenessof 350 ml. was diluted to a consistency of 0.6% and adjusted to a pH of4.5. Aliquots were withdrawn and treated with the materials shown in thetable, the pH after addition of the material or materials being adjustedto the value shown by the addition of NaOH or HCl as required. Tlhealiquots were gently stirred for ve minutes to allow adsorption of thesize to take place, after which sheets were formed on a Nash handsheetmachine, dried for one minute at 240 E., conditioned at 73 F., and 50%relative humidity for at least 24 hours, and tested for their water andink resistance by the Currier and BKY methods respectively.

Size

Percent Pulp Sheet Currier, BKY, Alum pH3 Basis See. Sec. No.1 PercentAdded:l Wt! Added2 8. 5 Nil 4. 5 43. 4 66 600 8. 5 Nil 4. 5 43. 4 64 6003. 5 Nil 4. 5 44. 1 29 353 5.0 Nl] 4. 5 47. 4 140 600 5.0 Nil 9. 0 44. 979 600 5. 0 Nil 4. 5 46. 8 67 600 5. 0 Nil 9. 0 46. 5 90 600 3. 5 Nil 4.5 43. 4 54 600 5. 0 N11 4. 5 44. 0 130 600 5. 0 3. 0 4. 5 45. 7 145 6005. 0 3.0 9. 0 44. 6 67 600 2. 0 Nil 4. 5 45. 1 35 0 3. 5 N11 4. 5 45. 561 600 1 Corresponds to sizes of table of Example 1. Based on dry weightoi the bers.

3 After addition of size.

4 Lb. per 25" x 40"/500 ream.

Slack scale.

The results indicate that an effective |amount of sizing takes placeboth when the fibers are formed into paper at alkaline as well as acidpH values. The results with size No. 7 show that the addition of |asmall amount of alum enhances the sizing effect obtained.

Example 3 The following illustrates a preferred method for manufacturingtwo typical .sizes of the present invention.

Size A.-1 mol of diethanolamine was reacted with 1.5 mols of technicalstea-ric acid and neutralized with 1.25 mols of glacial acetic acidaccording to Example 1. The molten ester salt was cooled and crushed toabout 10 mesh, and soaked for 6 hours in suflicient cold water toprovide a slurry having `a solids content of 7%. The 'slurry was rapidlyheated to 95 C. with rapid agitation. The slurry was cooled withcontinued agitation to room temperature and diluted to 5% solids byaddition of water.

Size B.-This size was prepared by reacting l mol of triethanolamine with2.5 mols of technical stearic acid, followed by the addition of 0.35 molof 37% aqueous HC1, according to the method for the preparation of SizeA.

The product was dispersed in water at 95 C. according to the methodemployed for the preparation of Size A.

When tested, both sizes gave somewhat superior results compared to thecorresponding sizes of Example l.

We claim:

1. Paper composed of cellulosic fibers sized by a uniformly adsorbentcontent within the range of about 1% to 4%, based on the weight of thelibers, of a product corresponding to that formed by heating 1 mol of anamine selected from the group consisting of the lower water-solubledialkanolamines, the lower water-soluble trialkanolamines and mixturesthereof with a saturated monocarboxylic fatty acid of 16-20 carbonatoms, the molar equivalence ratio of said fatty acid to the hydroxylgroups of said alkanolamine being between about 0.33 and 1.0, at anesterication temperature up to about 225 C. until reaction of said fattyacid with said alkanolamine is at least about 50% complete.

2. Paper according to claim 1 wherein the weight of the size is betweenabout 2% and 344% of the Weight of the fibers.

3. Paper according to claim 1 having an alkaline pH.

4. Paper composed of cellulosic fibers sized by a uniformly distributedcontent within the range of about 2% to 31/z%, based on the weight ofthe iibers, of a product corresponding to that formed by heating l molof a dialkanolamine with about 1.3 to 1.8 mols of a saturatedmonocarboxylic fatty acid of 16-20 carbon atoms a-t an estericationtemperature up to about 225 C. until reaction of the fatty acid is atleast complete.

5. Paper according to claim 4 wherein the dialkanolamine and the fattyacid are heated until reaction of the fatty acid is more than complete.

6. Paper according to claim 4 wherein the dialkanolamine isdiethanolamine and the fatty acid is stearic acid.

7. Paper composed of cellulosic fibers sized by a uniformly distributedcontent within the range of about 2% to 3%% based on the weight of thefibers of a product formed by heating 1 mol of a trialkanolamine withabout 2.0 to 2.5 mols of a saturated fatty acid of 16-20 carbon atoms atan estercation temperature up to about 225 C. until reaction of thefatty acid is at least 75% complete.

8. Paper according to claim 7, wherein the trialkanolamine and the fattyacid are heated until reaction of the fatty acid is more than 90%complete.

9. Paper according to claim 7, wherein the trialkanolamine istriethanolamine and the fatty acid is stearic acid.

10. Paper according to claim 7, wherein the trialkanolamine istriisopropanolamine and the fatty acid is stearic acid.

References Cited in the file of this patent UNITED STATES PATENTS2,332,226 Hutchins Oct. 19, 1943 2,492,702 Neubert et al Dec. 27, 19492,668,111 Lindquist Feb. 2, 1954 2,683,088 Reynolds July 6, 19542,710,285 Trusler June 7, 1955 OTHER REFERENCES Industrial & EngineeringChem., January 1941, pages 17 and 21. (Copy in Scientific Library.)

1. PAPER COMPOSED OF CELLULOSIC FIBERS SIZED BY A UNIFORMLY ABSORBENTCONTENT WITHIN THE RANGE OF ABOUT 1% TO 4%, BASED ON THE WEIGHT OF THEFIBERS, OF A PRODUCT CORRESPONDING TO THAT FORMED BY HEATING 1 MOL OF ANAMINE SELECTED FROM THE GROUP CONSISTING OF THE LOWER WATER-INSOLUBLEDIALKANOLAMINES, THE LOWER WATER-SOLUBLE TRIALKANOLAMINES AND MIXTURESTHEREOF WITH A SATURATED MONOCARBOXYLIC FATTY ACID OF 16-20 CARBONATOMS, THE MOLAR EQUIVALENCE RATIO OF SAID FATTY ACID TO THE HYDROXYLGROUPS OF SAID ALKANOLAMINE BEING BETWEEN ABOUT 0.33 AND 1.0, AT ANESTERIFICATION TEMPERATURE UP TO ABOUT 225* C. UNTIL REACTION OF SAIDFATTY ACID WITH SAID ALKANOLAMINE IS AT LEAST ABOUT 50% COMPLETE.